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. 2021 Jan 21;11(1):1956.
doi: 10.1038/s41598-021-81492-1.

Automatic recognition of uterine contractions with electrohysterogram signals based on the zero-crossing rate

Xiaoxiao Song  1 , Xiangyun Qiao  1 , Dongmei Hao  2 , Lin Yang  1 , Xiya Zhou  3 , Yuhang Xu  4 , Dingchang Zheng  4
Affiliations

Automatic recognition of uterine contractions with electrohysterogram signals based on the zero-crossing rate

Xiaoxiao Song et al. Sci Rep. .

Abstract

Uterine contraction (UC) is an essential clinical indicator in the progress of labour and delivery. Electrohysterogram (EHG) signals recorded on the abdomen of pregnant women reflect the uterine electrical activity. This study proposes a novel algorithm for automatic recognition of UCs with EHG signals to improve the accuracy of detecting UCs. EHG signals by electrodes, the tension of the abdominal wall by tocodynamometry (TOCO) and maternal perception were recorded simultaneously in 54 pregnant women. The zero-crossing rate (ZCR) of the EHG signal and its power were calculated to modulate the raw EHG signal and highlight the EHG bursts. Then the envelope was extracted from the modulated EHG for UC recognition. Besides, UC was also detected by the conventional TOCO signal. Taking maternal perception as a reference, the UCs recognized by EHG and TOCO were evaluated with the sensitivity, positive predictive value (PPV), and UC parameters. The results show that the sensitivity and PPV are 87.8% and 93.18% for EHG, and 84.04% and 90.89% for TOCO. EHG detected a larger number of UCs than TOCO, which is closer to maternal perception. The duration and frequency of UC obtained from EHG and TOCO were not significantly different (p > 0.05). In conclusion, the proposed UC recognition algorithm has high accuracy and simple calculation which could be used for real-time analysis of EHG signals and long-term monitoring of UCs.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
The influence of α on the recognition result.
Figure 2
Figure 2
The influence of γ on the recognition result.
Figure 3
Figure 3
Block diagram of recognition and evaluation of UCs with EHG and TOCO.
Figure 4
Figure 4
The configuration of the 8-electrodes on the abdomen.
Figure 5
Figure 5
Strengthening of EHG burst. (a) A sliding window moving along the elevated EHG signal. The zero-crossing points are in red, and the sliding window is in blue. (b) The zero-crossing rate. (c) Power of zero-crossing rate.
Figure 6
Figure 6
Recognition of UCs with EHG and TOCO. (a) Preprocessed EHG signal. (b) The modulated EHG signal. (c) Recognition of UCs with EHG envelope. (d) Recognition of UCs with TOCO signal.
Figure 7
Figure 7
The definition of UC duration.
See this image and copyright information in PMC

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